This illustration shows how photons in the Cosmic Microwave Background (CMB) are deflected by the gravitational lensing effect of massive cosmic structures as they travel across the Universe. Using data from ESA’s Planck satellite, cosmologists have been able to measure this gravitational lensing of the CMB over the whole sky for the first time.

Cosmologists have achieved a first detection of a long-sought component in the Cosmic Microwave Background (CMB). This component, known as B-mode polarisation, is caused by gravitational lensing, the bending of light by massive structures as it travels across the Universe. The result is based on the combination of data from the South Pole Telescope and ESA’s Herschel Space Observatory. This detection is a milestone along the way to the possible discovery of another kind of B-mode signal in the polarised CMB – a signal produced by gravitational waves less than a second after the Universe began.